Washing tablets marked with indicia on their surfaces

ABSTRACT

Washing tablets of compacted particulate washing composition are marked with indicia on their surfaces, the indicia preferably being of a contrasting color. Processes for applying the markings are also described, as is a combination of the marked tablets with a packaging system.

FIELD OF THE INVENTION

This invention relates to washing tablets marked with indicia on theirsurfaces and to processes for marking indicia on the surfaces of washingtablets. In addition, this invention relates to the marked tablets incombination with a packaging system.

BACKGROUND OF THE INVENTION

Washing compositions in tablet form (hereinafter referred to as “washingtablets”) are made from compacted particulate material. They are usedfor several applications, including laundry washing, machinedish-washing, toilet hygiene and bathing. Although this invention isprimarily directed at laundry and machine dish-wash tablets, it is alsoapplies to other types of washing tablets as will be apparent to theperson skilled in the art.

It is very well known to present indicia the surfaces of soap bars bymeans of an applied label bearing the indicia. However, it is notappropriate to label compacted particulate washing tablets in this waybecause the label will become detached in the wash cycle and could clogthe filter of the machine.

There are a number of options for manufacturing washing compositions,particularly those employed in laundry and machine dish-washing. Suchcompositions have for many years been manufactured in particulate form,commonly referred to as powders. More recently, washing compositionshave also been manufactured as liquids. Tablets, to which this inventionrelates, are yet another possibility.

Washing tablets have, potentially at least, several advantages overpowder and liquid products. They do not require the user to measure outa volume of powder or liquid. Instead, one or more tablets provide anappropriate quantity of the composition for the particular applicationto which the composition is directed. For example, one or more tabletswill provide an appropriate quantity of composition for washing a singleload in a laundry or dish-washing machine, or an appropriate quantity ofwashing composition in a vessel for bathing. Tablets are thereforeeasier for the consumer to handle and dispense, and being more compact,facilitate more economical storage.

Washing tablets are generally made by compressing or compacting aquantity of the washing composition in particulate form. Materials whichspecifically aid tablet formation can be added to the washingcomposition prior to compaction, however such materials are typicallyadded in small amounts and usually account for less than 10%, preferablyless than 5% by weight of the tabletted washing composition.

It is desirable that washing tablets should have adequate strength whendry, yet have the appropriate dispersion and dissolution characteristicsfor the particular function they are to perform. In the case of laundrytablets it is desirable that the tablets disperse and dissolverelatively quickly in the wash water. Generally speaking, washingtablets of the present invention disperse and dissolve significantlyquicker that other types of tablets. For example, most pharmaceuticaltablets are specifically designed to be delivered orally but not tobreak up and dissolve in the mouth, i.e. they are designed to dispenseand dissolve in the stomach and intestine. For this reason,pharmaceutical tablets have very different physical characteristics fromthose of washing tablets.

The colour of washing tablets is generally determined by the colour ofthe particulate ingredients being compacted. For example, colouredspecks may be added to a white powder to produce a speckled tablet, or ablue powder may be compacted to produce a blue tablet. In order toobtain a two-coloured “layered” tablet, two separate particulatecompositions need to be used. The colour may be the only difference incomposition between two layers in a washing tablet. In such a case,“layering” is used for aesthetic reasons and/or to indicate to theconsumer that the product performs two particular actions, i.e. it has a“double-action”. Clearly, in such cases, it would be advantageous if thetablet could be compacted from a single particulate composition andcolour applied to the formed tablet to give the appearance of layering.This would remove the need to have more than one particulate washingcomposition as starting material.

Manufacturers of washing tablets typically produce several variants oftablets, providing information regarding the particular variant on thetablet packaging. For example, in the case of laundry tablets, detailsof the brand name and brand type (e.g. non-biological, colour-care etc.)are usually found on the tablet packaging. This means that each tabletvariant has to have its own primary packaging appropriately labelled. Iftablets were marked with indicia indicating such details as brand nameand type, then the need to put this information on the tablet packagingwould be negated. Indeed, the same packaging could be used for all thevariants. Furthermore, transparent packaging would allow the markings onthe tablet to be observed through the packaging. This would offerconsiderable supply chain advantages, in particular in terms of time andcost savings.

It is known to use ink jet printing to print a picture, patterns and/orcharacters on a solid bath salt, as disclosed in JP-A-61 092696.However, bath salts do not present the same kind of technical problemfor surface marking, as do washing tablets.

To date, the skilled person has not succeeded marking washing tablets ontheir surfaces, and in particular laundry and machine-dish wash tablets,for a series of reasons. These include the following:

i) Washing tablets are prepared by compaction of relatively large coarseparticles. The compaction pressures are relatively low and the materialbeing compacted is primarily washing composition, i.e. no or relativelysmall amounts of ingredients specifically to aid tablet formation arepresent. As a result, washing tablets tend to have very rough undulatingsurfaces which have a tendency to rub off easily. This is one reason whywashing tablets are usually packaged individually or in pairs.Furthermore, the “undulations”, which to a certain extent are anartefact of the coarseness of the particulate starting material, arelarge relative to the size of the indicia one might wish to apply.

ii) Washing tablets are often made up of a multitude of components. Forexample, a laundry tablet may typically comprise surfactants, builders,sequestrants, soil-release agents, bleaches, fluorescers, enzymes,perfumes etc. Such a tablet would be prepared by mixing a number ofparticulate ingredients together to produce the right formulation andthen compacting the resulting particulate mixture. This results in alaundry tablet which differs dramatically in its chemical compositionacross its surface.

iii) Many washing tablets contain particular chemical components, suchas bleaches and dye transfer inhibitors, which could interact with acolourant used to mark the tablet.

iv) Many washing tablets have an alkaline pH, for example in excess of 9or even 10. Many colourants are pH sensitive.

v) Washing tablets are highly absorbent. This means that most solventshitting their surface will be absorbed very quickly, which in the caseof a colourant, could lead to a chromatography effect and loss ofdefinition. This would be highly undesirable.

vi) There is a need to ensure that any marking applied to the tabletsdoes not compromise the performance of the washing tablet. For example,in the case of a laundry tablet, if a colourant is used to mark indiciaon the tablet, this must not soil the clothes.

Surprisingly, in spite of the surface roughness, the surface's tendencyto rub off, the high absorbency and the variation in chemicalcomposition that can occur across the surface, we have found it ispossible to mark washing tablets with indicia on their surface and thatthe visibility and definition of the indicia produced are high andremain high for a significant length of time.

Clearly any marking process must not compromise the integrity of thetablets and be amenable to incorporation into a high-speed, automated,continuous production line. However, in order to perform their functionproperly (i.e. relatively rapid dispersion and dissolution), washingtablets are relatively less compact and less robust than other forms oftablets. Such inherent properties have been a major factor in dissuadingresearch on the feasibility of marking washing tablets with indicia ontheir surfaces. For example, see points (i) and (v) as discussed above.Thus, conventional techniques used to mark other types of tablets (e.g.pharmaceutical tablets) such as contact printing and engraving were notpreviously considered suitable for marking washing tablets, inparticular because of the lower mechanical strength of washing tablets.

Contrary to the perceived opinion, we have surprisingly found thatwashing tablets can be successfully marked with indicia, withoutdetriment to the integrity of the tablet, by use of conventional markingtechniques such as contact printing. More particularly, we have foundthat in various embodiments, the invention solves a number of differenttechnical problems, as will be described in more detail hereinbelow. Forexample, it has been found that non-contact marking techniques, such as,for example, ink-jet printing are particularly advantageous.

PRIOR ART

U.S. Pat. No. 4,548,825 discloses a method for marking tablets withletters or symbols using a ink-jet printing system. WO94/01239 describesa laser drilling process for producing holes in tablets. WO91/01884describes a process in which tablets are marked by contact printing andthen part of the printed mark removed by exposure to a laser. All thesedocuments relate to pharmaceutical tablets. Such tablets are morecompact than washing tablets, have much smoother surfaces than washingtablets and have surfaces with a far lower tendency to rub off thanwashing tablets. In addition, pharmaceutical tablets comprise relativelyfew components. They mainly comprise “filler” materials selected fortheir tablet making properties, to which are added relatively smallamounts of the pharmaceutical active. Consequently, the chemicalvariation across the surface of pharmaceutical tablets is far less thanthat observed in the washing tablets of the present invention.

DEFINITION OF THE INVENTION

In a first aspect, the invention provides a washing tablet of compactedparticulate washing composition having indicia on at least one surfacethereof.

In a second aspect, the invention provides a process for marking indiciaon the surface of a tablet of compacted particulate washing composition,characterised in that the indicia are applied by a contact markingtechnique.

In a third aspect, the invention provides a process for marking indiciaon the surface of a tablet of compacted particulate washing composition,characterised in that the indicia are applied by a non-contact markingtechnique.

In a fourth aspect, the present invention provides a combination of atleast one washing tablet of compacted particulate washing compositionhaving indicia on at least one surface thereof and a closed packagingsystem enclosing the at least one tablet.

DETAILED DESCRIPTION OF THE INVENTION

According to the first aspect of the present invention, the indiciais/are on at least one surface of the tablet. Preferably, such indiciais/are present directly on and/or in the surface, i.e., not on a labelwhich is applied to the surface but in direct contact with the tabletmaterial at that surface. As will be explained in more detailhereinbelow, alternative methods of achieving this can involve variousmethods of contact or non-contact printing, or forming a surface relieffeature, e.g. by etching.

TABLETS

Washing tablets of the present invention suitably have a mass of atleast 8 g, preferably at least 10 g, more preferably at least 15 g, andmay be up to 200 g or even 250 g, depending on the conditions ofintended use; for example, it may be a unit dose for an average load ina fabric washing or dishwashing machine, or a unit dose of bathing saltsfor a bath. Preferably, a laundry tablet is in the range 10 to 60 g,more preferably 15 to 50 g. Preferably, a machine dish wash tablet is inthe range 12 to 30 g, more preferably 15 to 27 g.

The tablets may be of any shape. However, for ease of packaging they arepreferably blocks of substantially uniform cross-section, such ascylinders or cuboids. The overall density of a tablet preferably lies ina range from 1000 up to 2000 g/l, more preferably up to 1800 g/l, yetmore preferably up to 1600 g/l. A laundry tablet may typically be in therange 1040 or 1050 up to 1300 g/l. A machine dish wash tablet densitymay typically be in the range of 1400 to 1600 g/l.

Tabletting

Tabletting entails compaction of a particulate washing composition. Avariety of tabletting machinery is known, and can be used. Generally itwill function by stamping a quantity of the particulate compositionwhich is confined in a die.

Tabletting may be carried out at ambient temperature or at a temperatureabove ambient which may allow adequate strength to be achieved with lessapplied pressure during compaction. In order to carry out the tablettingat a temperature which is above ambient, the particulate composition ispreferably supplied to the tabletting machinery at an elevatedtemperature. This will of course supply heat to the tablettingmachinery, but the machinery may be heated in some other way also.

If any heat is supplied, it is envisaged that this will be suppliedconventionally, such as by passing the particulate composition throughan oven, rather than by any application of microwave energy.

Typically, the particulate washing composition is exposed to acompaction pressure (i.e. force per unit area) of least 2,500 kN/m²,more preferably at least 4,000 kN/m². The maximum compaction pressureused in the manufacture of the washing tablets of the present inventionis less than 200,000 kN/m², preferably less 175,000 kN/m², morepreferably less than 150,000 kN/m², and most preferably less than100,000 kN/m².

Tabletting can be carried out using elastomeric coated dies as describedin WO98/46719 and WO98/46720 (Unilever).

Starting Material for Compaction

The particulate washing composition which is compacted may be a mixtureof particles of individual ingredients, but more usually will comprisesome particles which themselves contain a mixture of ingredients. Suchparticles containing a mixture of ingredients may be produced, forexample, by a granulation process or spray-drying process, and maycontain the surfactant and some or all of the detergency builder presentin any composition. Such particles may be used alone or together withparticles of single ingredients. Thus, a detergent tablet of thisinvention, or a discrete region of such a tablet, is a matrix ofcompacted particles.

Preferably the particulate composition has an average particle size inthe range from 200 to 2000 μm, more preferably from 250 to 1400 μm. Fineparticles, smaller than 180 μm or 200 μm may be eliminated by sievingbefore tabletting, if desired, although we have observed that this isnot always essential.

While the starting particulate composition may in principle have anybulk density, the present invention is especially relevant to tabletsmade by compacting powders of relatively high bulk density. Thus thestarting particulate composition may suitably have a bulk density of atleast 400 g/l, preferably at least 500 g/l, and possibly at least 600g/l.

Granular detergent compositions of high bulk density prepared bygranulation and densification in a high-speed mixer/granulator, asdescribed and claimed in EP 340013A (Unilever), EP 352135A (Unilever),and EP 425277A (Unilever), or by the continuousgranulation/densification processes described and claimed in EP 367339A(Unilever) and EP 390251A (Unilever), are inherently suitable for use inthe present invention.

Coatings

Tablets can also be coated either prior to being marked or aftermarking. Of course, if marked prior to being coated, the coating shouldbe sufficiently transparent to allow the indicia to be readily observed.This can be achieved by using an appropriate coating or by etching outan area of the coating to reveal or create the indicia.

Suitable coatings for tablets are, for example, those described inWO98/24873 (Procter & Gamble).

WASHING COMPOSITIONS

The present invention applies to a variety of different types of washingtablets. In addition to laundry and machine dish wash tablets, it isenvisaged that the present invention can be used to mark indicia on thesurfaces of any compacted particulate washing composition. Suitableexamples include bath salts, bath “bombs” and certain toilet blocks.

In a preferred embodiment, the washing tablets comprise a bleachcomponent.

In another preferred embodiment, the washing tablets have a pH of atleast 8.5, preferably at least 9, and more preferably at least 9.5. ThepH may be as high as 11.

Reference herein to the pH of a washing tablet is to a 1% (w/v) solutionof the tablet in demineralised water at 20° C.

Laundry Tablet Compositions Surfactant

Laundry tablets generally contain one or more detergent surfactants. Ina laundry washing composition, these preferably provide from 5 to 50 wt% of the overall tablet composition, more preferably from 8 or 9 up to40 or 50 wt % of the overall composition. Surfactant may be anionic(soap or non-soap), cationic, zwitterionic, amphoteric, nonionic or acombination of these.

Anionic surfactant may be present in an amount from 0.5 to 50 wt %,preferably from 2 or 4 up to 30 or 40 wt % of the tablet composition.

Synthetic (i.e. non-soap) anionic surfactants are well known to thoseskilled in the art. Examples include alkylbenzene sulphonates,particularly sodium linear alkylbenzene sulphonates; olefin sulphonates;alkane sulphonates; dialkyl sulphosuccinates; and fatty acid estersulphonates.

C₈₋₁₅ linear alkyl benzene sulphonates, and C₈₋₁₈, especially C₁₀₋₁₄,primary alkyl or alkenyl sulphates are commercially significant anionicsurfactants, especially the sodium salts. Frequently, such linear alkylbenzene sulphonates or primary alkyl sulphates, or a mixture thereofwill be the desired anionic surfactant and may provide 75 to 100 wt % ofany anionic non-soap surfactant in the composition.

In some forms of this invention the amount of non-soap anionicsurfactant lies in a range from 5 to 20 wt % of the tablet composition.

It may also be desirable to include one or more soaps of fatty acids.These are preferably sodium soaps derived from naturally occurring fattyacids, for example, the fatty acids from coconut oil, beef tallow,sunflower or hardened oils or fats.

Suitable nonionic surfactant compounds which may be used include inparticular the reaction products of compounds having a hydrophobic groupand a reactive hydrogen atom, for example, aliphatic alcohols, acids,amides or alkyl phenols with alkylene oxides, especially ethylene oxide.

Specific nonionic surfactant compounds are alkyl (C₈₋₂₂) phenol-ethyleneoxide condensates, the condensation products of linear or branchedaliphatic C₈₋₂₀ primary or secondary alcohols with ethylene oxide, andproducts made by condensation of ethylene oxide with the reactionproducts of propylene oxide and ethylene-diamine.

Especially preferred are the primary and secondary alcohol ethoxylates,especially the C₉₋₁₁ and C₁₂₋₁₅ primary and secondary alcoholsethoxylated with an average of from 5 to 20 moles of ethylene oxide permole of alcohol.

In certain forms of this invention the amount of nonionic surfactantlies in a range from 4 to 40 wt %, preferably 4 or 5 to 30 wt % of thecomposition. Many nonionic surfactants are liquids. These may beabsorbed onto particles of the composition, prior to compaction intotablets.

Detergency Builder

Laundry tablets will generally contain from 5, preferably from 15, up to80 wt % of detergency builder. Preferably, they will contain from 15 to60 wt % of detergency builder. This may be provided wholly by watersoluble materials, or may be provided in large part or even entirely bywater-insoluble material with water-softening properties.Water-insoluble detergency builder may be present at 5 to 80, preferably5 to 60 wt % of the composition.

Alkali metal aluminosilicates are strongly favoured as environmentallyacceptable water-insoluble builders for fabric washing. Alkali metal(preferably sodium) aluminosilicates may be either crystalline oramorphous or mixtures thereof, having the general formula:

0.8-1.5 Na₂O.Al₂O₃.0.8-6SiO₂ .xH₂O

These materials contain some bound water (indicated as xH₂O) and arerequired to have a calcium ion exchange capacity of at least 50 mgCaO/g. The preferred sodium aluminosilicates contain 1.5-3.5 SiO₂ units(in the formula above).

Suitable crystalline sodium aluminosilicate ion-exchange detergencybuilders are described, for example, in GB 1429143 (Procter & Gamble).The preferred sodium aluminosilicates of this type are the well knowncommercially available zeolites A and X, the newer zeolite P describedand claimed in EP 384070 (Unilever) and mixtures thereof.

Conceivably a water-insoluble detergency builder could be a layeredsodium silicate as described in U.S. Pat. No. 4,664,839. NaSKS-6 is thetrademark for a crystalline layered silicate marketed by Hoechst(commonly abbreviated as “SKS-6”). NaSKS-6 has the delta-Na₂SiO₅morphology form of layered silicate. It can be prepared by methods suchas described in DE-A-3,417,649 and DE-A-3,742,043. Other such layeredsilicates, such as those having the general formulaNaMSi_(x)O_(2x+1).yH₂O wherein M is sodium or hydrogen, x is a numberfrom 1.9 to 4, preferably 2, and y is a number from 0 to 20, preferably0 can be used.

Water-soluble phosphate-containing inorganic detergency builders,include the alkali-metal orthophosphates, metaphosphates, pyrophosphatesand polyphosphates. Specific examples of inorganic phosphate buildersinclude sodium and potassium tripolyphosphates, orthophosphates andhexametaphosphates.

Non-phosphate water-soluble builders may be organic or inorganic.Inorganic builders that may be present include alkali metal (generallysodium) carbonate; while organic builders include polycarboxylatepolymers, such as polyacrylates, acrylic/maleic copolymers, and acrylicphosphonates, monomeric polycarboxylates such as citrates, gluconates,oxydisuccinates, glycerol mono- di- and trisuccinates,carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates andhydroxyethyliminodiacetates, aminopolycarboxylates such asnitrilotriacetates (NTA), ethylenediaminetetraacetate (EDTA) andiminodiacetates, alkyl- and alkenylmalonates and succinates; andsulphonated fatty acid salts. This list is not intended to beexhaustive.

Laundry tablet compositions preferably include polycarboxylate polymers,more especially polyacrylates and acrylic/maleic copolymers which canfunction as builders and also inhibit unwanted deposition onto fabricfrom the wash liquor.

Bleach System

Laundry tablets may contain a bleach system. This preferably comprisesone or more peroxy bleach compounds, for example, inorganic persalts ororganic peroxyacids, which may be employed in conjunction withactivators to improve bleaching action at low wash temperatures. If anyperoxygen compound is present, the amount is likely to lie in a rangefrom 10 to 25 wt % of the composition.

Preferred inorganic persalts are sodium perborate monohydrate andtetrahydrate, and sodium percarbonate, advantageously employed togetherwith an activator. Bleach activators, also referred to as bleachprecursors, have been widely disclosed in the art. Preferred examplesinclude peracetic acid precursors, for example, tetraacetylethylenediamine (TAED), now in widespread commercial use in conjunction withsodium perborate; and perbenzoic acid precursors. The quaternaryammonium and phosphonium bleach activators disclosed in U.S. Pat. No.4,751,015 and U.S. Pat. No. 4,818,426 (Lever Brothers Company) are alsoof interest. Another type of bleach activator which may be used, butwhich is not a bleach precursor, is a transition metal catalyst asdisclosed in EP-A-458397, EP-A458398 and EP-A-549272. A bleach systemmay also include a bleach stabiliser (heavy metal sequestrant) such asethylenediamine tetramethylene phosphonate and diethylenetriaminepentamethylene phosphonate.

Other Detergent Ingredients

Laundry tablets may also contain one of the detergency enzymes wellknown in the art for their ability to degrade and aid in the removal ofvarious soils and stains. Suitable enzymes include the variousproteases, cellulases, lipases, amylases, and mixtures thereof, whichare designed to remove a variety of soils and stains from fabrics.Examples of suitable proteases are Maxatase (Trade Mark), as supplied byGist-Brocades N.V., Delft, Holland, and Alcalase (Trade Mark), andSavinase (Trade Mark), as supplied by Novo Industri A/S, Copenhagen,Denmark. Detergency enzymes are commonly employed in the form ofgranules or marumes, optionally with a protective coating, in amount offrom about 0.1 to about 3.0 wt % of the composition; and these granulesor marumes present no problems with respect to compaction to form atablet.

Laundry tablets may also contain a fluorescer (optical brightener), forexample, Tinopal (Trade Mark) DMS or Tinopal CBS available fromCiba-Geigy AG, Basel, Switzerland. Tinopal DMS is disodium4,4′bis-(2-morpholino-4-anilino-s-triazin-6-ylamino)stilbenedisulphonate; and Tinopal CBS is disodium2,2′-bis-(phenyl-styryl)disulphonate.

An antifoam material is advantageously included, especially if a laundrytablet is primarily intended for use in front-loading drum-typeautomatic washing machines. Suitable antifoam materials are usually ingranular form, such as those described in EP 266863A (Unilever). Suchantifoam granules typically comprise a mixture of silicone oil,petroleum jelly, hydrophobic silica and alkyl phosphate as antifoamactive material, sorbed onto a porous absorbed water-solublecarbonate-based inorganic carrier material. Antifoam granules may bepresent in an amount up to 5% by weight of the composition.

It may also be desirable that a laundry tablet includes an amount of analkali metal silicate, particularly sodium ortho-, meta- or disilicate.The presence of such alkali metal silicates at levels, for example, of0.1 to 10 wt %, may be advantageous in providing protection against thecorrosion of metal parts in washing machines, besides providing somemeasure of building and giving processing benefits in manufacture of theparticulate material which is compacted into tablets. A composition forlaundry washing will generally not contain more than 15 wt % silicate.

Further ingredients which can optionally be employed in laundry washingtablets include anti-redeposition agents such as sodiumcarboxymethylcellulose, straight-chain polyvinyl pyrrolidone and thecellulose ethers such as methyl cellulose and ethyl hydroxyethylcellulose, fabric-softening agents; heavy metal sequestrants such asEDTA; perfumes; and colorants or coloured speckles.

Machine Dish-Wash Tablet Compositions Surfactant

Machine dish-wash tablets preferably contain a surfactant systemcomprising a surfactant selected from nonionic, anionic, catonic,ampholytic and zwitterionic surfactants and mixtures thereof.

Typically the surfactant is a low- to non-foaming nonionic surfactant,which includes any alkoxylated nonionic surface-active agent wherein thealkoxy moiety is selected from the group consisting of ethylene oxide,propylene oxide and mixtures thereof, is preferably used to improve thedetergency without excessive foaming. However, an excessive proportionof nonionic surfactant should be avoided. Normally, an amount of 15 wt %or lower, preferably 10 wt % or lower, more preferably 7 wt % or lower,most preferably 5 wt % or lower and preferably 0.1 wt % or higher, morepreferably 0.5 wt % or higher is quite sufficient, although higher levelmay be used.

Examples of suitable nonionic surfactants for use in the invention arethe low- to non-foaming ethoxylated straight-chain alcohols of thePlurafac® RA series, supplied by the Eurane Company; of the Lutensol® LFseries, supplied by the BasF Company and of the Triton® DF series,supplied by the Rohm & Haas Company.

Other surfactants such as anionic surfactant may be used but may requirethe additional presence of antifoam to surpress foaming. If an anionicsurfactant is used it is advantageously present at levels of 2 wt % orbelow.

Detergency Builder

Machine dish-wash tablets generally contain a builder. The builder maybe a phosphate or non-phosphate builder and typically is present at alevel of from 1 to 90, preferably from 10 to 80, most preferably from 20to 70 wt % of the composition.

Specific examples of water-soluble phosphate builders are the alkalimetal tripolyphosphates, sodium, potassium and ammonium pyrophosphate,sodium and potassium orthophosphate, sodium polymeta/phosphate in whichthe degree of polymerization ranges from about 6 to 21, and salts ofphytic acid. Sodium or potassium tripolyphosphate is most preferred.

Suitable examples of water-soluble non-phosphate inorganic buildersinclude water-soluble alkali metal carbonates, bicarbonates,sesquicarbonates, borates, silicates, including layered silicates suchas SKS-6 ex. Hoechst, metasilicates, and crystalline and amorphousaluminosilicates. Specific examples include sodium carbonate (with orwithout calcite seeds), potassium carbonate, sodium and potassiumbicarbonates, silicates including layered silicates and zeolites.

Organic detergent builders can also be used as non-phosphate builders.Examples of organic builders include alkali metal citrates, succinates,malonates, fatty acid sulfonates, fatty acid carboxylates,nitrilotriacetates, oxydisuccinates, alkyl and alkenyl disuccinates,oxydiacetates, carboxymethyloxy succinates, ethylenediaminetetraacetates, tartrate monosuccinates, tartrate disuccinates, tartratemonoacetates, tartrate diacetates, oxidized starches, oxidizedheteropolymeric polysaccharides, polyhydroxysulfonates, polycarboxylatessuch as polyacrylates, polymaleates, polyacetates, polyhydroxyacrylates,polyacrylate/polymaleate and polyacrylate/polymethacrylate copolymers,acrylate/maleate/vinyl alcohol terpolymers, aminopolycarboxylates andpolyacetal carboxylates, and polyaspartates and mixtures thereof. Suchcarboxylates are described in U.S. Pat. Nos. 4,144,226, 4,146,495 and4,686,062. Alkali metal citrates, nitrilotriacetates, oxydisuccinates,acrylate/maleate copolymers and acrylate/maleate/vinyl alcoholterpolymers are especially preferred non-phosphate builders.

Water Soluble Polymeric Polycarboxylic Compounds

A water-soluble polymeric polycarboxylic compound is advantageouslypresent in machine dish wash compositions at a level of at least 0.1 wt%, more preferably at levels from 1 to 7 wt % of the total composition.

Preferably these compounds are homo- or co-polymers of polycarboxyliccompounds, especially co-polymeric compounds in which the acid monomercomprises two or more carboxyl groups separated by not more than twocarbon atoms. Salts of these materials can also be used.

Particularly preferred polymeric polycarboxylates are co-polymersderived from monomers of acrylic acid and maleic acid. The averagemolecular weight of these polymers in the acid form preferably rangesfrom 4,000 to 70,000.

Another type of polymeric polycarboxylic compounds suitable for use inthe composition of the invention are homo-polymeric polycarboxylic acidcompounds with acrylic acid as the monomeric unit. The average weight ofsuch homo-polymers in the acid form preferably ranges from 1,000 to100,000 particularly from 3,000 to 10,000.

Acrylic sulphonated polymers as described in EP 851 022 (Unilever) arealso suitable.

Silicates

Machine dish wash tablets can optionally comprise alkali metalsilicates. The alkali metal may provide pH adjusting capability andprotection against corrosion of metals and against attack on dishware,including fine china and glassware benefits.

When silicates are present, the SiO₂ level should be from 1 to 25,preferably from 2 to 20, more preferably from 3 to 10%, based on theweight of the total composition. The ratio of SiO₂ to the alkali metaloxide (M₂O, where M=alkali metal) is typically from 1 to 3.5, preferablyfrom 1.6 to 3, more preferably from 2 to 2.8. Preferably, the alkalimetal silicate is hydrous, having from 15 to 25% water, more preferablyfrom 17% to 20%.

The highly alkali metasilicates can in general be employed, although theless alkaline hydrous alkali metal silicates having a SiO₂:M₂O ratio offrom 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of thealkali metal silicates with a SiO₂:M₂O ratio of 2.0 or more are alsoless preferred because they tend to be significantly less soluble thanthe hydrous alkali metal silicates having the same ratio.

Sodium and potassium, and especially sodium, silicates are preferred.While typical forms, i.e. powder and granular, of hydrous silicateparticles are suitable, preferred silicate particles having a meanparticle size between 300 and 900 microns and less than 40% smaller than150 microns and less than 5% larger than 1700 microns. Particularlypreferred is a silicate particle with a mean particle size between 400and 700 microns with less than 20% smaller than 150 microns and lessthan 1% larger then 1700 microns. Compositions of the present inventionhaving a pH of 9 or less preferably will be substantially free of alkalimetal silicate.

Enzymes

Enzymes may be present in machine dish wash compositions. Examples ofenzymes suitable for use in the cleaning compositions of this inventioninclude lipases, peptidases, amylases (amylolytic enzymes) and otherswhich degrade, alter or facilitate the degradation or alteration ofbiochemical soils and stains encountered in cleansing situations so asto remove more easily the soil or stain from the object being washed tomake the soil or stain more removable in a subsequent cleansing step.Both degradation and alteration can improve soil removal.

Well-known and preferred examples of these enzymes are lipases, amylasesand proteases. The enzymes most commonly used in machine dishwashingcompositions are amylolytic enzymes. Preferably, the composition of theinvention also contains a proteolytic enzyme. Enzymes may be present ina weight percentage amount of from 0.2 to 5 wt %. For amylolyticenzymes, the final composition will have amylolytic activity of from 10²to 10⁶ Maltose units/kg. For proteolytic enzymes the final compositionwill have proteolytic enzyme activity of from 10⁶ to 10⁹ GlycineUnits/kg.

Bleach Material

Bleach material is preferably present in machine dish was compositions.The bleach material may be a chlorine- or bromine-releasing agent or aperoxygen compound. Peroxygen based bleach materials are howeverpreferred.

Organic peroxy acids or the precursors therefor are typically utilizedas the bleach material. The peroxyacids usable in the present inventionare solid and, preferably, substantially water-insoluble compounds. By“substantially water-insoluble” is meant herein a water-solubility ofless than about 1 wt % at ambient temperature. In general, peroxyacidscontaining at least about 7 carbon atoms are sufficiently insoluble inwater for use herein.

Inorganic peroxygen-generating compounds are also typically used as thebleaching material of the present invention. Examples of these materialsare salts of monopersulphate, perborate monohydrate, perboratetetrahydrate, and percarbonate.

Monoperoxy acids useful herein include alkyl peroxy acids and arylperoxyacids such as peroxybenzoic acid and ring-substitutedperoxybenzoic acids (e.g. peroxy-alpha-naphthoic acid); aliphatic andsubstituted aliphatic monoperoxy acids (e.g. peroxylauric acid andperoxystearic acid); and phthaloyl amido peroxy caproic acid (PAP).

Typical diperoxy acids useful herein include alkyl diperoxy acids andaryldiperoxy acids, such as 1,12-di-peroxy-dodecanedioic acid (DPDA);1,9-diperoxyazelaic acid, diperoxybrassylic acid, diperoxysebacic acidand diperoxy-isophthalic acid; and 2-decyldiperoxybutane-1,4-dioic acid.

Peroxyacid bleach precursors are well known in the art. As non-limitingexamples can be named N,N,N′,N′-tetraacetyl ethylene diamine (TAED),sodium nonanoyloxybenzene sulphonate (SNOBS), sodium benzoyloxybenzenesulphonate (SBOBS) and the cationic peroxyacid precursor (SPCC) asdescribed in U.S. Pat. No. 4,751,015.

If desirably a bleach catalyst, such as the manganese complex, e.g.Mn-Me TACN, as described in EP-A-0458397, or the sulphonimines of U.S.Pat. No. 5,041,232 and U.S. Pat. No. 5,047,163, is to be incorporated,this may be presented in the form of a second encapsulate separatelyfrom the bleach capsule or granule. Cobalt catalysts can also be used.

Among suitable reactive chlorine- or bromine-oxidizing materials areheterocyclic N-bromo and N-chloro imides such as trichloroisocyanuric,tribromoisocyanuric, dibromoisocyanuric and dichloroisocyanuric acids,and salts thereof with water-solubilizing cations such as potassium andsodium. Hydantoin compounds such as 1,3-dichloro-5,5-dimethyl-hydantoinare also quite suitable.

Particulate, water-soluble anhydrous inorganic salts are likewisesuitable for use herein such as lithium, sodium or calcium hypochloriteand hypobromite. Chlorinated trisodium phosphate and chloroisocyanuratesare also suitable bleaching materials.

Encapsulation techniques are known for both peroxygen and chlorinebleaches, e.g. as described in U.S. Pat. No. 4,126,573, U.S. Pat. No.4,327,151, U.S. Pat. No. 3,983,254, U.S. Pat. No. 4,279,764, U.S. Pat.No. 3,036,013 and EP-A-0,436,971 and EP-A-0,510,761. However,encapsulation techniques are particularly useful when using halogenbased bleaching systems.

Chlorine bleaches, the compositions of the invention may comprise fromabout 0.5 to about 3% avCl (available Chlorine). For peroxygen bleachingagents a suitable range are also from 0.5 to 3% avO (available Oxygen).Preferably, the amount of bleach material in the wash liquor is at least12.5×10⁻⁴ and at most 0.03% avO by weight of the liquor.

Chelating Agent

A chelating agent may be present in a machine dish wash composition. Ifpresent, it is preferable if the level of chelating agent is from 0.5 to3 wt % of the total composition.

Preferred chelating agents include organic phosphonates, aminocarboxylates, polyfunctionally-substituted compounds, and mixturesthereof.

Particularly preferred chelating agents are organic phosphonates such as^(α)-hydroxy-2 phenyl ethyl diphosphonate, ethylene diphosphonate,hydroxy 1,1-hexylidene, vinylidene 1,1 diphosphonate, 1,2dihydroxyethane 1,1 diphosphonate and hydroxy-ethylene 1,1diphosphonate. Most preferred is hydroxy-ethylene 1,1 diphosphonate.

Anti-Tarnishing Agents

Anti-tarnishing agents such as benzutriazole and those described in EP723 577 (Unilever) may also be included.

Optional Ingredients

Optional ingredients are, for example, buffering agents, reducingagents, e.g., borates, alkali metal hydroxide and the well-known enzymestabilisers such as the polyalcohols, e.g. glycerol and borax;anti-scaling agents; crystal-growth inhibitors, threshold agents;thickening agents; perfumes and dyestuffs and the like.

Reducing agents may e.g. be used to prevent the appearance of anenzyme-deactivating concentration of oxidant bleach compound. Suitableagents include reducing sulphur-oxy acids and salts thereof. Mostpreferred for reasons of availability, low cost, and high performanceare the alkali metal and ammonium salts of sulphuroxy acids includingammonium sulphite ((NH₄)₂SO₃), sodium sulphite (Na₂SO₃), sodiumbisulphite (NaHSO₃), sodium metabisulphite (Na₂S₂O₃), potassiummetabisulphite (K₂S₂O₅), lithium hydrosulphite (Li₂S₂O₄), etc., sodiumsulphite being particularly preferred. Another useful reducing agent,though not particularly preferred for reasons of cost, is ascorbic acid.The amount of reducing agents to be used may vary from case to casedepending on the type of bleach and the form it is in, but normally arange of about 0.01 to about 1.0, preferably from about 0.02 to about0.5 wt % will be sufficient.

Disintegration Aids

In a preferred embodiment, washing tablets of this invention containingredients which promote disintegration of the tablets in their washingapplication. For example, the tablets can contain ingredients which leadto the generation of a gas upon contact with water (i.e. generate aneffervescent effect) such as citric acid and sodium bicarbonate.Alternatively or in addition, the tablets can contain water-swellablepolymeric material and/or disintegration-promoting particles asdescribed in WO98/55582, WO98/55583 and WO98/55590 (Unilever).

MARKING AND INDICIA

The washing tablets of the present invention have indicia on theirsurface(s). These indicia can take numerous forms. They can be words,symbols, pictures, patterns, logos, combinations of these, or simplyzones of colour. The manufacturers name, the brand name and the brandtype are typical examples of what can be marked on the tablet.Furthermore, instructions for use and/or safety instructions can bemarked on the tablets.

The provision of written or pictorial instructions for use and/or safetyinstructions on the surface of washing tablets is new and has notpreviously been reported. Using the process of the present inventionthis is now achievable. In particular, the ability to be able to placesafety instructions on washing tablets may be important. Somecompositions, especially machine dish wash compositions, may containingredients which can irritate both through touch and breathing,although this does not generally apply to laundry tablets.

In a preferred embodiment, the indicia are of a contrasting colour tothe surface of the washing tablet. In a preferred embodiment, thecontrasting colour is provided by a colourant comprising a pigmentand/or dye.

As mentioned earlier, tablets can be given the appearance of layering bymarking the formed tablet with a zone of colour. This providesconsiderable cost savings over current methods of producing “layered”tablets. Of course, more than one colour can be applied by the processof the invention and intricate patterns if desired.

Colourants

Colourants can be either a solution or a suspension of a colouringagent. As used herein the term ink is taken to mean a solution of a dyeor a suspension of a pigment in a carrier vehicle. The colourant istherefore preferably an ink. Inks are prepared by suspending ordissolving the dye or pigment in a liquid, volatile carrier such aswater, alcohol, or mixture thereof. Suitable alcohols include loweralkanols such as methanol, isopropanol, butanol, isobutanol or ethanol,and polyols such as glycol, polyethyleneglycol or glycerol.

For better fixing on the surfaces, an adhesive may be employed. Suitableexamples include sugar-based adhesives such as methyl cellulose,hydroxypropyl methylcellulose or hydroxypropyl ethylcellulose phthalate.

Water-based inks contain from 70 to 90% water depending on the nature ofthe ink. However, because of the small droplet size, the solventevaporates rapidly and does not affect the structure of the washingtablet.

Clearly, the final usage of the washing tablet has to be taken intoconsideration when selecting the nature of the ink and the particularcolorant being used. If the tablet is to be used for washing laundry,then obviously a colorant which is liable to damage clothing in the washenvironment is unsuitable.

Colourants which are pH stable, especially those which arealkali-stable, are particularly suited to the present invention. In apreferred embodiment inks comprising alkali-stable dyes are used to markwashing tablets with a alkaline pH, e.g. laundry and machine dish washtablets. An example of an alkali-stable dye is Solar Yellow GB 300%C119555.

Pigments tend not to be effected by high or low pH values to the samedegree as many dyes. Thus in another preferred embodiment, inkscomprising pigments are used to mark washing tablets with a alkaline pH,e.g. laundry and machine dish wash tablets. Suitable pigments, forexample, include Flexo Yellow GRX, Mostryl Blue, Tinofil Carmine andKenalake Green.

Furthermore, pigments are typically less likely to be effected bybleaches than dye-based colourants.

Marking Process

Tablets can be marked on their surface using a contact or non-contactmarking technique.

Contact Marking

Surprisingly, we have found that washing tablets can be marked withindicia, such as for example a brand name, by contact printing. This canbe achieved using either a dye based ink or a pigment based ink.

We have found that the problems associated with the uneven surface andrelatively low strength of the washing tablets can to a large extent beovercome by using an appropriately elastic die.

Thus, in a preferred embodiment, the device for contact printing thewashing tablet comprises a die, the die having at least one tablet“stamping” surface wherein the tablet stamping surface comprises, atleast in part, an elastomeric material. Preferably, any part of thetablet stamping surface which is intended to come into contact with thetablet surface, i.e. those parts of the die which define and impart themarking (e.g. logo), comprise an elastomeric material.

Suitable dies may comprise an elastomeric portion and a non-elastomericportion. If this is the case, the elastomeric portion must be the onethat contacts the surface of the washing tablet. In a preferredembodiment, the elastomeric portion comprises one or more coatings whichare adhered or attached to a non-elastomeric portion.

By “elastomeric” according to the invention is meant a material asdefined in ISO (International Standard Organisation) 1382 as an“elastomer”, or a “rubber”. Also included in the definition of“elastomeric” materials according to the invention are thermoplasticelastomers and copolymers and blends of elastomers, thermoplasticelastomers and rubbers.

Elastomers are defined as polymers with long flexible chains,independent in the raw material and transformed via vulcanising orcross-linking agents which introduce cross-links and form a cross-linkednetwork structure. The network structure retains the movement of themacro-molecular chain molecules and as a result returns rapidly toapproximately its initial dimension and shape after deformation by aforce and release of the force.

With increasing temperature an elastomer goes through a rubbery phaseafter softening and retains its elasticity and elastic modulus until itsdecomposition temperature is reached.

Thermoplastic elastomers consist of amorphous and crystalline phases.The amorphous phase has a softening range below ambient temperature andthus acts as an elastic spring whilst the crystalline segments whosesoftening range is above ambient temperature, act as cross-linking sites

Preferably the elastomeric material according to the invention isselected from those classes described in American Society for Testingand Materials D1418 which include:

1. Unsaturated carbon chain elastomers (R Class) including naturalrubbers e.g. Standard Malaysian Rubber; butadiene e.g. “BUNA” type exBunawerke Huls; and butadiene acrylonitrile copolymer e.g. “Perbunan” exBayer.

2. Saturated carbon chain elastomers (M Class) includingethylene-propylene types e.g. “Nordel” ex DuPont and fluorine containingtypes e.g. “Viton” ex DuPont.

3. Substituted silicone elastomers (Q Class) including liquid siliconerubbers e.g. Silastic 9050/50 P (A+B) ex Dow Corning.

4. Elastomers containing carbon, nitrogen and oxygen in the polymerchain (U Class) including polyurethanes e.g. polyurethanes ex Belzona.

Suitable elastomeric materials include silicone rubbers such as Silastic9050/50 P A+B (ex Dow Corning) which after curing has a modulus ofelasticity about 2-3 MPa; and polyurethanes, for example Belzona PU2221,as hereinafter defined, which after curing has a modulus of elasticityof about 9 MPa, and Belzona 2131 (MP Fluid Elastomer), a 2 part productbased on a diphenylmethane 4,4′-diisocyanate (MDI) system with aphenylmercuric neodecanoate catalyst.

If being used to coat a die surface, the “elastomeric” material, ashereinbefore defined, may be pretreated, such as by forming a solutionof a commercially available elastomer, prior to it being applied as acoating on the die surface. The elastomers, rubbers, and copolymers andblends thereof are generally cured or cross-linked, in-situ on the diesurface. For example, the components including the base elastomericmaterial, cross-linking agents and other materials such as acceleratorsmay be mixed prior to application as a coating. Once applied to the diethe coatings are cured in-situ. This maybe aided by the application ofheat or other accelerating processes, for example pressure; radiation orUV light.

In some cases, materials may be dissolved with an appropriate solvent,applied to the die and the solvent subsequently driven off.

In the case of themoplastic materials, they can be heated to meltcondition applied to the die, cooled and resolidified.

The modulus of elasticity of the surface of the die which comes intocontact with the surface of the washing tablet may be measured byrecording the force required to indent the elastomeric material as afunction of the indentation depth. Typically an indentor with aspherical tip may be employed and the slope, s, of the force as afunction of the indentation depth to the power 3/2 is determined. Theindentation depth is the movement of an indentor into the elastomericmaterial after it first contacts the surface of the material. Ingeneral, it is necessary to correct the measured indentation depth forthe compliance of the measurement apparatus. That is, the actualindentation depth, d, is related to the measured apparent value d′ bythe following expression

d=d′−(F.C)

where F is the indentation force. The compliance C is determined bycompressing the indentor against a rigid surface and recording theapparent displacement as a function of the applied force which has aslope equal to C. The modulus of elasticity E is calculated from thefollowing expression$E = {\frac{3}{4} \cdot s \cdot \frac{1}{\sqrt{R}} \cdot \left( {1 - b^{2}} \right)}$

where s=F/d^(3/2), R is the radius of the spherical tip of the indentorand b is the Poisson's ratio of the elastomeric material which is equalto about 0.5 for elastomers.

Under certain conditions to be described hereafter, the aboveindentation method may give falsely large values of the elastic modulusdue to the influence of the rigid material to which the elastomericmaterial is attached. This may be a particular problem when theelastomeric material has been applied as a thin coating. In order tosafely avoid this problem it is necessary to ensure that the contactradius of the indentor with the elastomeric material does not exceedabout {fraction (1/10)} of the thickness of the material, e.g. thecoating. The contact radius, a, is related to the indentation depth bythe following expression

a={square root over (dR)}

If the elastomeric material is a coating, it is preferred that it is atleast 200 μm, more preferably at least 500 μm, yet more preferably 1 mmthick. Of course, it will be understood that thinner coatings may stillprovide benefits, for example in the case where tablets with relativelysmooth surfaces are being marked.

Preferably, the surface of the die which comes into contact with thesurface of the washing tablet has a modulus of elasticity of less than5×10⁷ Nm⁻², preferably less than 1×10⁷ Nm⁻². The modulus of elasticityis preferably greater than 1×10⁵ Nm⁻², more preferably greater than1×10⁶ Nm⁻², and yet more preferably greater than 3×10⁶ Nm⁻². Preferably,the modulus of elasticity is in the range 5×10⁶ to 1×10⁷ Nm⁻².

Non-Contact Marking

In another preferred embodiment, tablets are marked with indicia ontheir surface using a non-contact marking technique. Using suchtechniques, tablets can be marked on any area of their surface which isexposed, i.e. which is not in immediate or very near contact with anysupporting or conveying means. This is not possible withcontact-printing techniques since they require the tablet to beresilient to a certain degree to the contact force in order for a goodprint mark to be imparted.

Any appropriate non-contact technique may be used as will be apparent tothe person skilled in the art. However, two techniques are particularlypreferred.

Ink-Jet Printing

Printing by means of an ink-jet process is well-known in the art inrelation to printing on paper and the like.

In the present invention, ink is dotted by means of an ink-jet processonto the surface of a washing tablet so that, as a result of controlledguidance and/or deflection, multiple dots of ink are applied on thesurface of the tablet so as to form an indicia.

The ink-jet printer produces an image by propelling from a printer heada stream of fine droplets which impact on the surface of the tablet tobe marked, preferably as the tablet is conveyed past the head. Thedroplets are controlled, typically electrically, so that they aredeposited in a controlled array and the tablet surface is thereby markedwith a desired indicia. Several different types of ink-jet printers areavailable, the major difference being in the method of propelling theink onto the surface to be marked.

Each small droplet of ink produces a tiny dot on the tablet surface.More often than not, multiple droplets are applied at the same positionby applying the ink in pulses. This allows the colour intensity of a dotto be built up without increasing the size of the dot to a great extentand thus losing definition. By applying dots in close proximity to oneanother, a readily visible image is built up.

Laser-Marking

Laser marking is achieved by removing material from the tablet surfaceto be marked or by changing the surface of the tablet. The mostimportant consideration is how well the material being marked absorbsthe laser beam. This can determine the type of laser beam used asdifferent wavelengths can have different absorption characteristics.

For optimum results the laser beam should be absorbed in the very outersurface of the tablet so that sufficient energy density is produced tomodify the surface by one of the following three processes:

i) Coating removal: The laser is absorbed by the surface coating andvaporises it to reveal a contrasting substrate. For example, a tabletsurface may be coloured using an ink-jet process and part of thecolorant subsequently removed using a laser.

ii) Etching: The laser vaporises material from the surface of the tabletwithout producing any colour change. The resulting mark looks similar toan embossed print.

iii) Thermochemical: The laser changes the material by heating it to asufficiently high temperature to break molecular bonds. The new materialformed by this process may have a different colour thus producing adiscernible mark.

The first two processes both rely of removal of material form thesurface of the tablet by vaporisation. In this sense they are both aform of etching. Any suitable mode of etching can be used in the presentinvention as will be obvious to the skilled man. Three examples of modesof etching are as follows:

i) The laser beam can be passed through a mask or stencil precut withthe desired marking. The laser beam, which forms an image of the mask,is then directed onto the surface of the tablet to be marked. Suitablelasers include those which have been designed for industrial markingapplications and which produce short, powerful pulses of light energy,preferably in the infrared range, e.g. carbon dioxide and helium-neonlasers. Preferably, the pulsed lasers are used at a low pulse energy buthigh repetition rate in order to achieve a high, industrially viablemarking speed.

ii) The tablet can be moved past a plurality of pulsed laser beamsarranged along a single line, thus creating a dot matrix pattern on thesurface of the tablet.

iii) The laser beam can be scanned over the surface of the tablet usingrapidly rotating, computer-controlled mirrors. Suitable lasers for usein this mode are continuous wave carbon dioxide lasers.

The vaporised portion of the tablet surfaces can be removed by suctionusing well-known devices in the art.

Tablet Production Process

The washing tablets are preferably produced by a continuous processwhich includes the steps of compaction, conveyance and packaging.

In a preferred embodiment, the marking process and apparatus are fullyautomated. Preferably, they are also controlled via a computer.

Ideally, the marking process and apparatus are fully integrated into theprocess for washing tablet manufacture, being positioned somewherebetween the compaction and packaging steps. Preferably, marking takesplace during the conveying step.

Preferably, the compaction, conveyance, marking and packaging steps arecontrolled through an integrated control system, preferably by means ofa computer.

Conveyance

Tablets are conveyed by an appropriate conveying means from thecompaction step to the packaging step. A typical conveying meanscomprises a conveyor belt, which may optionally have means for holdingthe washing tablets in position, particularly if the tablets are of anunusual shape.

The marking or printing equipment will preferably be positioned alongthe conveying means, preferably above and/or to the side of the passingwashing tablets. Preferably the marking or printing equipment isequipped with a sensor to detect when a tablet is passing it; typicallyunderneath and/or to the side of it. Once the leading edge of a tabletis detected, the marking or printing device is triggered to mark thetablet.

Of course, if the tablets are uniformly spaced and are being conveyed ata constant rate, it is not essential to have a sensor to detect theleading edge of each tablet; the marking or printing equipment couldsimply be triggered at set time intervals.

Packaging

The invention provides a combination of at least one tablet of compactedparticulate washing composition marked on its surface with indicia and aclosed packaging system enclosing the at least one tablet.

Preferably the packaging system is an easy to open system in which thetablet or tablets may be easily articulated while still within thepackaging. Furthermore, the packaging system will preferably includemeans for, or be designed to facilitate, easy dispensing of the tablettherefrom, preferably without the need for the user to handle orotherwise physically contact the tablet composition.

One way of achieving this is to package one or more washing tablets in aflow wrap packaging system whereby, once the system has been opened, thetablets may simply be squeezed out of the package and directly into adispensing device or apparatus of application. Further, the seals on theflow wrap may be sufficiently weakened at strategic points to allow sucha squeezing or forcing action to open the flow wrap package.

An alternative method which is envisaged is the provision of acylindrical container having an opening at one end thereof and areclosable lid means for the opening whereby dispensing of the washingtablets is effected by simply removing the lid and inverting thecontainer until a tablet falls out into a dispensing device.

Preferably, the packaging system has a moisture vapour transmission rate(MVTR) of less than 20 g/m²/24 hours. Ideally, the MVTR is approximately5 g/m²/24 hours.

The packaging system will advantageously have some permeability tooxygen. Preferably, this will not be greater than 2000 cm³/m³/24 hours.

Typically, the packaging system comprises a material having a bulkdensity of less than 40 g/m².

Preferably, the packaging system comprises a polymeric film, preferablyan oriented polypropylene film. Suitable films are sold under thetrademark BICOR. Alternatively, the packaging system may comprise aPET/PE laminate, preferably having a thickness of approximately 12micron PET/40 micron PE.

In a preferred embodiment of the invention the washing tablet is wrappedin a flow-wrap sealed polymer-based packaging system such as thosedescribed above. Ideally, the flow-wrap is heat sealed at each end alonga longitudinal seam.

In another embodiment of the invention, the packaging system cancomprise a water soluble wrapping, and preferably a thermoformed watersoluble packaging material. Such materials are well known in the art.

In a preferred embodiment, the combination according to the inventionwill ideally comprise two washing tablets wrapped in a flow-wrappackaging system.

The packaging system is preferably at least partially transparent. In apreferred embodiment, if the tablets are marked with words or symbolsindicative of the origin of the tablet (e.g. the manufacturer's name,the brand, etc.) or with safety instructions or instructions for use,the packaging is at least sufficiently transparent for these markings tobe clearly visible to the eye.

The invention is now further illustrated by the following non-limitingexamples:

EXAMPLES Example 1

In Example 1, a conventional laundry tablet was marked using an ink-jetprinter. The tablets were Persil Non-Bio for the UK market. Thesetablets were cylindrical in shape, the height being about half thecircumference. The tablets were marked with the logo “Persil” on an endsurface.

The ink-jet printer was a Domino A300 series. The ink was Domino 432-RDfood grade ink. The following machine settings were used: 16, 21 and 32drops using the 75 μm nozzle. The speed of the machine at each settingwas 68, 29 and 13 m/min, respectively.

The logo in each case was well-defined and remained so for severalweeks.

Example 2

The following pigments/dyes were used to contact print a design onPersil Non-Bio laundry tablets for the UK market:

Solar yellow BG 300% C119555 (dye)

Flexo Yellow GRX (pigment)

Monstryl Blue (pigment)

Tinofil Carmine (pigment)

Kenalake Green (pigment)

Tablets were marked by coating the die/stamp with dye or pigment andthen pressing the dye onto the surface of the tablet with a small amountof pressure.

Half the tablets were stored for 6 weeks in natural light; half in adark cupboard. Storage was at ambient temperatures. The colours showedno degradation over this timescale.

What is claimed is:
 1. A process for marking indicia on the surface of atablet of compacted particulate washing composition, characterised inthat the indicia are applied by a non-contact marking technique, inwhich the non-contact marking technique comprises ink-jet printing.
 2. Aprocess for marking indicia on the surface of a tablet of compactedparticulate washing composition, characterised in that the indicia areapplied by a non-contact marking technique, in which the non-contactmarking technique comprises laser marking.